Coupling for cathode-ray tubes



Patented May 20, 1952 COUPLING FOR CATHODE-RAY TUBES Rene Barthelemy, Fontenay aux Roses, France, assignor to Compagnie Pour `La Fabrication des Compteurs et Materiel dUsines a Gaz, Montrouge, France Application March 21, 1946, Serial No. 655,977 In France `November 17, 1942 Section 1, PuhlicLaW 690, August 8, 13946 Patent expires November 17, 1962 2 Claims.

The present invention is relating to a coupling device for the projection tube in a television receiver.

It is already known that it is necessary to use a very high accelerating voltage for the projection of television images `by means of cathode ray oscillograph tubes. This voltage must be of the order of 50 to 100 kv. Consequently, the construction of these oscillograph tubes vis especially diicult and costly, owing .to the fact that the deviationelements are necessarily located in the immediate vicinity of the neck of the tube. This involves considerable contour distances and thickness for the insulating material employed. In order to avoid these drawbacks, the anode of the cathode ray oscillograph tube is connected in such manner that it is ata potential which is approximately equal to that of ground and masses in the immediate proximity thereof, whereby it results that the cathode and the control grid of the oscillograph `tube have a very high negative potential with respect to ground.

The advantage of this arrangement is, that no great potential difference exists between `the deiiection members and the portions of the )tube located in their vicinity; therefore flashing over the contour and piercing of the Wall of the tube are denitely avoided. But the modulation of tubes connected in this way cannot be achieved as usual by a capacity-resistance coupling, because of the great size and prohibitive cost of the coupling condenser. The latter should be constructed for operation under a voltage equal to the total accelerating voltage.

The object of the present invention is to obviate this disadvantage.

It essentially consists, on the one hand, in modulating, by the voltage intended to modulate the projection tube, i. e. by the image modulation the current delivered by an oscillator functioning on metric or decimetric wave lengths and, on the other hand, in insulating the control grid of the projection tube relatively to the modulating means by means of an inductive or capacitive coupling, set in an insulating medium, the electrical length of the line between the modulating means and the coupling means being either an odd multiple of a quarter of a wave length in the case of inductive coupling, or an even multiple of a quarter of a wave length in Figures 1 and 2 are relative respectively to two particular realizations of the coupling means provided in a device according to the invention.

Figures 3 and 4 show two arrangements of devices according to the invention.

An inductive ,coupling is represented in Fig. 1. Ina `tank l lled with a suitable insulating matter, either solid or liquid, is placed an inductive coupling constituted e. g. by two parallel bars 2 and 3. Bar 2 is connected to the anodes of the output tubes V4 and 5 Vof a modulated high frequency source. Bar.3 is connected to the projection tube Ithrough conductors 6 and 1. Such a coupling .allows a free passage for Ythe modulated high frequency energy and insures, `from the standpoint of potentials, a separation be- .tween the high potential elements connected to :barZ and theconductorsand .1 of necessarily a rather low potential.

Fig. 2 shows an analogous arrangement in the case Aof `a Vcapacitive coupling, which comprises two condensers 48 and B. The electrical length of the line between the `modulated high frequency `source and the condensers 8 and 9 should'be in preference equal to an even multiple of a quarter of a Wave length of the high frequency be effected by means of diodes or suitable multielectrode tubes. The modulation voltage thus collected may be applied to the modulating electrode of the projection tube.

The use of metric or decimetrc waves oiers the advantage of necessitating but an equipment of a reduced size, all the same allowing for the transmission of extremely wide bands of modulation. An additional advantage in using very short waves is that the dimensions of the coupling elements between the portions of the feeding lines, which are at a low potential and the lines at a high potential, are very much reduced.

Fig. 3 shows one arrangement according to this invention. The image-modulation is applied, via wires I2, to a modulator I3, so as to modulate the current at the elevated frequency furnished by oscillator I4. This modulated current is led to coupling means I of the type already described, and of which two embodiments are shown in Figs. 1 and 2. The voltage modulated at high frequency, derived from the coupling means I5 is applied between cathode I6 and modulation electrode I1 of the projection cathode ray oscillograph I8. A suitable bias applied to modulation electrode I1, obtained for eX- ample by the resistor I9 and a source of direct current (not shown), allows the realization of internal detection in the oscillograph as has been above explained.

In the embodiment of Fig. 4 detection is produced by suitable well-known means 20.

What I claim is:

1. In a television receiver including a cathode ray oscillograph, the combination of means comprising a circuit traversed by image-modulation current, an oscillator producing waves of the order of one meter in length, a modulator connected to the said circuit and to the said oscillator to modulate the oscillations thereof by the image-modulation current, two wires connected yto the output of said modulator, and traversed by the modulated oscillations formed by the said modulator, connecting means to the cathode and the modulation electrode of the said oscillograph, inductive coupling means including therein a, primary and a secondary element, the exvtremities of said primary element being connected respectively to said wires and said secondary element being connected to said connecting means, the length of said wires between the said modulator and the said primary element being an odd multiple of a quarter of a wave length of said oscillator, and means for detecting the image-modulation in the modulated current furnished by said coupling means.

2. In a television receiver including a cathode ray oscillograph, the combination of means comprising a circuit traversed by image-modulation current, an oscillator producing waves of the vorder of one meter in length, a modulator connected to said circuit and to said oscillator, so as to modulate the oscillation thereof by the image-modulation current, two wires connected to the output of said modulator and traversed by the modulated oscillations formed by the said modulator, connecting means to the cathode and to the modulation electrode of the said oscillograph, inductive coupling means comprising two parallel bars, the extremities of one of said bars being connected respectively to said wires and the extremities of the other bar being connected to said connecting means, the length of said wires between the said modulator and the said bar connected to said wires being an odd multiple of a quarter of a wave length of said oscillator, and means for detecting the image-modulation in the modulated current furnished by said coupling means.

vRENE BARTHELEMY.

' REFERENCES CITED The following references are of record in the le of this lpatent:

UNITED STATES PATENTS OTHER REFERENCES Practical Analysis of Ultra High Frequency, RCAv (1943). 

